One method to control intake and exhaust valve operation during engine operation is described in French patent application. No. FR 2851367 A1. This method presents several means to control a dual coil electromagnetically actuated valve. One approach described in the application attempts to open and close an electrically actuated valve using a single coil of a dual coil actuator, the closing coil. By controlling current to a single coil, the amount of energy used to operate an engine with electrical valves may be lowered. In addition, impacts between valve components may be reduced by controlling a valve with a single coil. This method of controlling a valve is sometimes referred to as “Ballistic” mode.
The above-mentioned method can also have a disadvantage. Namely, the method may be limited to a narrow range of engine operating conditions because the valve opening lift amount and duration may not be controllable during some operating conditions by using a single coil. By controlling a dual coil actuator with a single coil, the valve may not be held in an open position long enough for the cylinder to induct enough air to support combustion. Consequently, this method of valve control may be limited to engine operating conditions where torque and speed are relatively low. On the other hand, the valve may stay open longer than desired, at least during some conditions. For example, during idle conditions a low torque amount may be necessary to hold an engine at a desired idle speed. Due to valve timing, the amount of air and fuel that is inducted into a cylinder may be able to produce torque in excess of the torque necessary to maintain the desired idle speed. Consequently, engine torque may be regulated by other means such that a fraction of the total torque available from the air-fuel mixture is produced. As a result, fuel consumption and emissions may increase.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method of electromechanical valve control that offers substantial improvements.